The present invention relates to fastening means, in particular to positive connecting means, as for example clips for fastening of clothing strips to flat rods.
Modern textile processing machines, in particular, cards are furnished with different carding segments, depending on the process stage. Stationary carding segments and/or carding rods to the carding segments of the card belong, in particular, in the pre-carding and re-carding zone and the carding segments. Most cards nowadays are furnished with revolving flat aggregates, i.e., they possess revolving flat rods. Cards with stationary flats and, respective, stationary flat rods are less common. With cards, it is common to furnish the flat or revolving flat rods with so-called clothing strips. The clothing strips are furnished with flexible or semi-rigid clothing, which differ from all steel clothing and/or saw tooth type clothing in such a way, that they are inserted and/or punched individually, or as U-shaped double hooks, into more or less flexible fabric and plastic layers.
The clothing strips are attached with fastening means, so-called clips or clothing strip clips, to the carding rods of the carding segments. Various clips of the state of the art are shown, for example, in the disclosures U.S. Pat. No. 5,755,012, U.S. Pat. No. 5,898,978 and DE 513728. Such an arrangement is, for example, also shown in FIG. 1. The clips 1 are made of sheet metal and/or steel and they advantageously simplify the fastening and replacing of the clothing strips 2 onto the flat rods 3. The clips 1 have the function of fixedly clamping the clothing strips 2 onto the flat rods. They do this by establishing a positive connection between the clothing strip and the flat rod. Normally, the clips are employed in pairs, so that a clip is to ensure for respective clamping on both sides of the flat rod (see FIG. 1). On one side, the clips have teeth 4. These teeth 4 are inserted and/or punched into the clothing strips 2 (illustrated in FIG. 1 with a broken line). Thereby, these teeth 4 are positively connected with the clothing strip. The other side 5 of the clips is pressed around the rib 6 of the flat rod 3 by applying a suitable tool. Thus, the clips 1 firmly clamp the clothing strips 2 to the flat rod 3 over its entire length. This type of fastening has proved successful in the past. The clips can be attached very easily to the flat rods with a suitable tool and can also be easily removed again.
The carding rods, and in particular the flat rods for the card, were formerly manufactured in the form of a—usually T-shaped—cast iron. Recently they have also been manufactured in the form of hollow profiles (extruded profiles) of light metal and/or light metal alloys (e.g., flat rod 3 in FIG. 1). Aluminum is often used as a material for the production. The carding segments co-operate with rotary rollers, as do the flat rods, which co-operate with the cylinder of the card. Thereby, the carding rods or flat rods must be somewhat longer than the working width of the card, so that they can rest on the adjustable flex bends on the left and on the right side of the cylinder and can be transported (or, in the case of stationary flat rods, be fastened thereon). The flat rods are exposed to a relatively high mechanical load (shearing load) applied through their carding work. Therefore, they must have a high stability or rigidity, in order not to deflect or deform during operation.
The carding quality, and thus the quality of the produced card web, depends substantially on the set carding gap (space between the clothing of the flat rods and the clothing of the cylinders). This carding gap is nowadays adjusted within the range of tenth of millimeters. Usually, it measures between 0.2 and 0.3 mm, depending on the processed fibre material and the desired carding quality. It can be observed that the tendency in the spinning mills points in the direction of setting or adjusting the carding gap within ever more narrow ranges. Carding gap settings of 0.15 mm represent at the present the rather extreme case, however, such narrow settings might be wished in the future more frequently by spinning mills. Therefore, the accurate setting of the carding gap is very important. It is, therefore, understood that fluctuations and inaccuracies in the adjusted space have considerable negative effects on the quality of the carding process. For the carding process it is very important that the carding gap over the entire work area within which carding work is done can be adjusted evenly. For example, the carding gap must be accurately adjusted over the total length of the flat rods and over the whole area of the flat (i.e., within the work area of all flat rods being arranged one behind the other). The narrower, however, the carding gap is chosen, the more difficult it is to adjust it and to keep it constant. The narrower the range gets within which the carding gap is to be kept, the more sensitive the flat area reacts, with the set carding gap, to each effect and to each change, like for example temperature fluctuations. The carding gap is adjusted and/or checked during standstill with a feeler gauge. Usually this setting takes place once in each case after each adjustment of the flats of the card, for example, after maintenance (the replacement of the flats) or in the case of a change of the processed material (fiber material to be treated newly often requires another carding gap adjustment). Adjusting of the flats actually always takes place on the “cold machine”, i.e. at normal ambient temperature, which can differ, depending on the location of the machine within the spinning mill, between 20 and 30 degrees Celsius. During operation of the card, the operating temperatures at the flat rods, depending on the air conditioning, can amount to between 20 degrees Celsius (during starting period of the machine) and 40 degrees Celsius (with a warm machine and bad air conditioning within the spinning mill). It is understood that the carding gap, even with such temperature fluctuations, is always to be held at the desired value. However, the narrower the carding gap needs to be adjusted, the more sensitive is the reactions of the carding process to changes of the gap.
Recently, the flat rods have been made of light metal, in particular of aluminum, and/or of light metal alloys as extruded hollow profiles, produced by extrusion method (see FIG. 1). Such flat rods are provided with solid headpieces at their two ends. Examples of such flat rods can be seen in the disclosures DE 43 04 148 A1, EP 627,507 B1 or U.S. Pat. No. 4,827,573. The headpieces are usually positively connected with the aluminum profile and have a machined bearing surface, which slides accurately and with low friction on the sliding guides of the card (flex bends). In the case of revolving flat rods, the headpieces are furthermore connected with the drive components of the flat aggregate, e.g., with a driving chain or a driving belt. This design has a number of advantages in comparison to the older type flat rods made as casting. In particular, they can be manufactured more simply and cheaper.
The use of light metal or light metal alloys as material for the flat rods can, however,—under certain operating conditions—also have disadvantages. With such types of flat rods up to now, common type clips made of sheet metal or steel were used. Measurements now revealed that these flat rods can deform when the temperature rises to the operating temperature in the card. The reason for this is that the clips are mounted onto the flat rods at room temperature. In the case of a temperature rise of the card to the operating temperature, the mounted flat rods resume a concave type of shape seen in their longitudinal direction, so that the carding gap is larger in the center of the flat rod than at its end. Thus, the carding process can be impaired. The impairment of the carding process is the more serious the narrower the carding gap is set and the longer the flat rods are. With the carding gap settings applied nowadays, it should therefore be avoided that the flat rods become bent.